纤维鞘特异性蛋白Vad1.2在精子发生中的作用及其分子机制的研究

Male infertility affects about 7% of male population. It is of great significance to identify the underlying genetic causes of male infertility, not only for identifying the etiologic factors leading to defective spermatogenesis, but also for the development of etiology-based diagnosis and therapy. Spermatogenesis involves complex cell-cell interactions between somatic cells and germ cells that are regulated by steroid hormones which in turn induce expression of a cascade of genes responsible for the growth, proliferation and differentiation of spermatogonia to form mature haploid spermatozoa. The tail of mature sperm contains fibrous sheath which not only provides mechanical support for the tail, but also plays an important role in the regulation of sperm motility. Dysplasia of fibrous sheath is commonly found in patients with asthenozoospermia. We have identified a novel testis-specific protein, Vad1.2, which is abundantly expressed in the fibrous sheath. To unveil the role of Vad1.2 in spermatogenesis, we generated Vad1.2 knockout mice. Our preliminary data showed that the mice with Vad1.2 deficiency had smaller testis, reduced sperm count and motility, and bending of tail in the principal piece, indicating the important role of Vad1.2 in spermatogenesis, particularly on tail formation. This project aims to further investigate the function and molecular mechanism of Vad1.2 in the formation of fibrous sheath. And also aims to explore the role of Vad1.2 in human semen anomalies by studying the expression of Vad1.2 in normal and asthenozoospermic sperm. This project may provide fundamental information on how fibrous sheath defects affect sperm quality and better our understanding of poor sperm quality due to tail defects which may provide treatment regimen for infertile patients with semen anomalies.

男性不育症的发病率高达7%，须对生精机制深入了解才能实现对其根本性治疗。纤维鞘是精子尾部重要的附属结构，对尾部结构维持、能量代谢、活力调控等起着重要作用，其发育不良可导致人精子尾部形态异常、活力低下或缺失。纤维鞘形成的分子机制目前尚不明确。Vad1.2是一个新发现的纤维鞘特异性蛋白，为探明其生理功能，我们制作了Vad1.2基因敲除小鼠。先期获得的3只Vad1.2-/-雄性小鼠的初步结果显示其睾丸偏小，附睾尾精子数偏少，活力低下，且大部分尾部呈折叠状态，表明Vad1.2在精子发生中起着重要作用。本课题将以Vad1.2-/-雄性小鼠为模型，系统揭示Vad1.2在精子发生特别是纤维鞘形成中的作用及其分子机制。此外，还将对Vad1.2在正常人及弱精症患者精子的表达进行检测，探讨Vad1.2与男性精子功能障碍的关系。本研究结果对男性精子发生和功能障碍的研究以及男性不育症的治疗具有重要意义。

男性不育症的发病率高达7%，须对生精机制深入了解才能实现对其根本性治疗。纤维鞘是精子尾部重要的附属结构，对尾部结构维持、能量代谢、活力调控等起着重要作用，其发育不良可导致人精子尾部形态异常、活力低下或缺失。纤维鞘形成的分子机制目前尚不明确。Vad1.2是一个新发现的纤维鞘特异性蛋白，为探明其生理功能，我们制作了Vad1.2基因敲除小鼠用以探明Vad1.2在精子发生以及纤维鞘形成中的作用及其分子机制。相对于野生型小鼠，Vad1.2-/-雄性小鼠生殖力明显下降，且其睾丸重量、附睾精子数目及活力均明显减少。约有一半的附睾精子形态异常，在尾部中段/主段连接处或主段呈折叠状态。Vad1.2缺失还导致纤维鞘结构发育异常，同时伴随着粗纤维和轴丝的结构异常。此外，免疫共沉淀结果显示Vad1.2与另一个重要的纤维鞘特异性蛋白Akap4相互结合，并且两者在精子发生过程中呈现出相似的表达模式。而Akap4蛋白前体pro-Akap4 和成熟蛋白mature-Akap4在突变型小鼠睾丸中明显升高，表明Vad1.2可能与Akap4共同参与到纤维鞘的形成，而pro-Akap4与mature-Akap4在突变型睾丸升高则有可能是对Vad1.2缺失的一种应激反应。本研究基本阐明了Vad1.2在精子发生特别是纤维鞘形成过程中的作用机制，对进一步扩展我们对精子发生的认识具有重要意义。